This invention relates to a system adapted for analyzing the permeation of a gas or vapor through a film or membrane, more particularly the rate of such permeation.
Some films are used to prevent or inhibit the permeation of certain gases either out of an environment, or into a certain environment. Membranes are often used to separate certain components, in some cases certain gases. Both membranes and films are used to either prevent the permeation of a certain gas, or separate gas mixtures. The rate of permeation of a certain gas through such film or membrane is a critical factor. Films used to prevent the permeation of one component either out of or into an environment find use in many areas; barrier packaging, agricultural films, industrial hygiene, and the like.
In one particular embodiment, agricultural films are used to minimize the loss of soil fumigant to the atmosphere by providing a physical barrier to the fumigant. To determine the efficacy of such films in such use, the rate of permeation of the particular fumigant through the film is critical. A device built by M. J. Kolbezen has been developed for measuring such rates of permeation. See Kolbezen et al Pesticide Science, 3, 67-71 (1972); and Kolbezen et al Pesticide Science, 3, 73-80 (1972) (both incorporated herein by reference in relevant parts). Within the agricultural films industry this device and the measurement of the rate of permeation that it affords, now called the Kolbezen, are recognized as the standard in the art.
The Kolbezen device suffers from some deficiencies, in that the Kolbezen device allows for the measurement of a rate of permeation wherein the pressure on both sides of the film are equal. In many applications the pressure on either side of the film is different thereby effecting the rate of permeation. Further, the Kolbezen device measures the rate of permeation wherein the temperature on both sides of the film is equivalent. In may environments the temperature on either side of the film is significantly different. The failure to account for such differences results in the measurement of permeation rates in an environment which does not reflect actual usage conditions.
What is needed is a means for measuring the rate of permeation of a gas or vapor through a film or membrane wherein the pressure on either side of the membrane or film is different. What is further needed, is a method for measuring the rate of permeation of a gas or vapor through a film or membrane wherein the temperature on either side of the film or membrane is different.